During the last decade microaerophilic spiral to curved shape bacteria isolated from the stomach of humans and animals have been the focus of considerable research because of their association with gastric disease (32). These microorganisms are now recognized as belonging to the genus Helicobacter. It is now known that the species Helicobacter pylori causes active, chronic gastritis and peptic ulcer disease in humans (1,25,32). This microorganism has also been recently linked to the development of gastric adenocarcinoma and gastric mucosal associated lymphoma (22,33,35,47). Several additional species of Helicobacter that have been isolated from the stomachs of various mammalian species (13,16,23,31) and have been shown to cause varying degrees of gastritis in their hosts (20,21,24). Additional species of Helicobacter have been isolated from the intestinal tracts of mammals (1,17,42,44) and birds (15). One of these, H. muridarum primarily colonizes the ileum and cecum of rodents, but can also apparently elicit a gastritis after colonizing the gastric mucosa of older rodents (1,2). Also, "Helicobacter (Flexispira) rappini" has been associated with abortion in sheep and intestinal disease in animals and humans (12,27,39). Most recently "H. rappini" has been isolated from the colon and cecum of mice (41).
Helicobacter species are often commensal bacteria in the gastrointestinal tract or are associated with chronic diseases in humans and animals (1). In humans, H. pylori has been associated with chronic, active gastritis, peptic ulcer and gastric carcinoma. Other Helicobacter organisms cause gastritis naturally in ferrets (H. mustelae), dogs and cats (H. fells) and cheetahs, (H. acinoynx) (2). Helicobacter species colonizing the lower GI tract of mice and causing no apparent disease include H. muridarum and "H. rappini", although H. muridarum can under certain conditions also colonize the stomach of mice and induce gastritis (2).
Campylobacter jejuni infections have been associated with rare hepatitis in humans (8) and in mice experimentally inoculated with selected strains of C. jejuni (9). Chronic active hepatitis in humans (10) and dogs (11) is sometimes caused by Leptospires.
The present invention provides the discovery of a novel species of Helicobacter (Helicobacter hepaticus) that colonizes experimental mice. The prevalence of this Helicobacter infection in experimental research colonies throughout the United States is not known. It is possible, because of shipment of mice to other facilities over the past two years, that infected mice may have been distributed elsewhere. The potential complications to research by this insidious chronic infection are significant. No routine serologic test is available at present to diagnose this infection. Because this infection produces no clinical signs and may only be apparent in older mice, it is of utmost importance to screen mouse colonies by serology and histologic examination of liver sections for these organisms. Thus, methods for diagnosing Helicobacter hepaticus infection are provided.